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Biomedical subjects

R K Webb

Publications and source records attributed to R K Webb.

At least 55 records · Page 3Linked to original sources
PubMed1993

The Australian Incident Monitoring Study. Paediatric incidents in anaesthesia: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) were analysed to compare anaesthetic incidents in infants and children with those in adults. Of the 2000, 1790 (90%) involved adults, 151 (7%) children and 56 (3%) infants. Healthy children (ASA I) generated a greater proportion of incidents in this group than adults and infants, emphasizing the need for maintaining the same standards for children in this group as for infants and higher risk groups. The AIMS results are similar to those of the United States (US) paediatric "closed claims" studies; the paediatric subset in both the US study and AIMS made up 10% of the total. Also, in both studies, incidents involving the respiratory and breathing circuit systems accounted for nearly half the problems, and cardiovascular problems and problems with the anaesthetic machine each accounted for 10-14% of incidents. In the AIMS study procedures on the head and neck yielded proportionately more incidents in the infant/child group than in the adult group, as did incidents involving the respiratory and breathing circuit systems. Incidents in the child group were often detected clinically; however, there were no differences between the three age groups in the way monitors were used or performed; hence the same monitoring recommendations apply to all groups. Combined oximetry and capnography would have detected nearly 90% of all applicable problems in the AIMS study and could have prevented nearly 90% of the claims arising from inadequate ventilation in the US "closed claims" study.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Physical injuries and environmental safety in anaesthesia: an analysis of 2000 incident reports.

Of the first 2000 incidents reported to the Australian Incident Monitoring Study, 56 (3%) involved environmental hazards or injuries to patients or staff. There were 17 cases of oral trauma (14 of tooth loss or damage, in 7 of which poor dentition played a role), 10 incidents involving problems with the operating table, 6 cases of skin or eye damage and 6 cases in which an electrical hazard was identified. Five incidents occurred during transport, and there were 4 cases of monitor induced trauma, 4 "needlestick" injuries and 4 miscellaneous incidents. Recommendations are made for trying to avoid or reduce the incidence of some of these problems.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Problems associated with vascular access: an analysis of 2000 incident reports.

There were 65 incidents involving access to the vascular system amongst the first 2000 reported to the Australian Incident Monitoring Study. Thirty-three involved peripheral venous access (14 cases of extravascular extravasation, 8 of unintended arterial cannulation, 6 of disruptions to intravenous lines, and 5 of problems with infusion lines, taps, pumps and connectors). Eighteen cases involved central venous access (9 cases of arterial puncture with haematomas, 5 with morbidity and/or prolonged admission), 5 of catheter misplacement and pneumo- or hydro-thorax and 4 of problems arising from operator inexperience. Thirteen cases involved peripheral arterial access (5 involved equipment problems (3 with possible air embolism), 3 of mistaking an arterial for a venous line (drugs were injected in 2), 3 of losing arterial lines or signals, and 2 in which the presence of an arterial line placed the patient at risk). The anaesthetist should always question the continued integrity of any vascular access system, even when it has recently been shown to be functioning, and the possibility of later "migration" and misplacement should always be borne in mind. Whenever possible, correct placement of the tip should be checked (e.g. by visual inspection of the site, use of test doses, aspiration of blood, pressure measurement, X-rays). When there is more than one line, all lines and sites of access (e.g. 3-way taps) should be clearly labelled and checked before anything is injected or infused.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Equipment failure: an analysis of 2000 incident reports.

Of the first 2000 incidents reported to the Australian Incident Monitoring Study, 177 (9%) were due to "pure" equipment failure according to pre-defined criteria. Of these 107 (60%) involved anaesthetic equipment, 42 (24%) involved monitors, 17 (10%) other theatre equipment and 11 (6%) the gas or electricity supply. Ninety-seven (55% of the 177) were potentially life-threatening; of these two-thirds would be detected by the array of monitors recommended by the Australian and New Zealand College of Anaesthetists and all but 9 of the remainder would be handled by application of the crisis management algorithm recommended elsewhere in this symposium. Of the 9 remaining, 2 were electrical shock, 3 overheating of a humidifier or blood warmer, 2 the unavailability of a spare laryngoscope and 1 the consequence of a power failure. Meticulous adherence to the equipment checking and monitoring guidelines of the Australian and New Zealand College of Anaesthetists and application of a suitable crisis management algorithm should protect the patient from potentially life-threatening equipment failure in virtually all cases except electric shock, power failure and overheating of warming devices.

Anesthesiology↗
PubMed1993

The Australian Incident Monitoring Study. Human failure: an analysis of 2000 incident reports.

Information of relevance to human failure was extracted from the first 2,000 incidents reported to the Australian Incident Monitoring Study (AIMS). All reports were searched for human factors amongst the "factors contributing," "factors minimising", and "suggested corrective strategies" categories, and these were classified according to the type of human error with which they were associated. In 83% of the reports elements of human error were scored by reporters. "Knowledge-based errors" contributed directly to about one-quarter of incidents; the outcome of one third of incidents was thought to have been minimised by prior experience or awareness of the potential problems, and in one fifth some strategy to improve knowledge was suggested. Correction of "rule-based errors" or provision of protocols or algorithms were thought, together, to have a potential impact on nearly half of all incidents. Failure to check equipment or the patient contributed to nearly one-quarter of all incidents, and inadequate crisis management contributed to a further 1 in 8. "Skill-based errors" (slips and lapses) were directly responsible for 1 in 10 of all incidents, and were thought to make an indirect contribution in up to one quarter. "Technical errors" were responsible for about 1 in 8 incidents. Analysing the relative contribution of each type of error for each type of problem allows the development of rational preventative strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. System failure: an analysis of 2000 incident reports.

Although 70-80% of problems have some component of human error, its overall contribution to many problems may be small; studies of complex systems have revealed that up to 85% are primarily due to deficiencies in the lay-out and processes of the system. The anaesthetist has to operate in a complex system; many problems originate from deficiencies in this system. Information of relevance to system failure was extracted from the first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS). A system-based deficiency directly contributed to one-quarter of problems (four-fifths if human factors are included), some aspect of the system minimized the adverse outcome in over half of all cases (four-fifths if human factors are included), and in two-thirds (three-quarters if human factors are included) a system-based strategy would have been helpful; the system was implicated in 90% of all incidents (97% if human factors are included). Regardless of whether or not all human error should be regarded as part of the "system", attempts to modify its incidence and nature have to emanate from the system. AIMS reporting pathways and the organizations involved in developing and implementing strategies to improve the system operate at four levels. Level I involves the use of AIMS reports by hospitals and group practices for audit at a local level. Level II involves AIMS participants sending forms to the AIMS central office; collated information is then sent back to contributors by newsletter. Level III involves interaction between AIMS and the major professional bodies and level IV interaction between AIMS, these bodies and a variety of national and international agencies. Over 100 topics were identified from the AIMS data for consideration at one or more of these levels. AIMS has the potential not only to play a vital practical role in the continued enhancement of the quality of anaesthetic practice, but also to provide a valuable resource for research at the increasingly important interface between human behaviour and complex systems.

Accidents↗
PubMed1992

Ventilation/perfusion indices do not correlate with the difference between oxygen consumption measured by the Fick principle and metabolic monitoring systems in critically ill patients.

OBJECTIVE: To determine whether the difference between oxygen consumption (VO2) measured by metabolic gas monitoring systems and by the Fick principle is related to venous admixture, deadspace/tidal volume ratio, or alveolar-arterial oxygen tension gradient in critically ill patients. DESIGN: A prospective study. SETTING: An 11-bed general ICU in a 900-bed teaching hospital. PATIENTS: Twenty critically ill patients admitted to the ICU who required mechanical ventilation, right heart catheterization, and arterial and mixed venous gas measurements for normal clinical management. RESULTS: Thirty-three recordings were analyzed. The mean VO2 measured by the metabolic gas monitoring system was 308 +/- 63.9 (SD) mL/min and was significantly greater than the mean VO2 measured by the Fick principle of 284 +/- 72.0 mL/min. The difference between the two measurements of 24.3 +/- 47.6 mL/min correlated poorly with venous admixture (r2 = .0009), dead-space/tidal volume ratio (r2 = .0064) and alveolar-arterial oxygen tension gradient (r2 = .017). CONCLUSIONS: If the difference in VO2 measured by metabolic gas monitoring systems and the Fick principle is due to intrapulmonary VO2 then in critically ill patients the ventilation/perfusion indices of venous admixture, deadspace/tidal volume ratio and alveolar-arterial oxygen tension gradient correlate poorly with intrapulmonary VO2.

Adult↗
PubMed1992

A longitudinal study of 100 consecutive admissions for carbon monoxide poisoning to the Royal Adelaide Hospital.

A longitudinal study of one hundred consecutive admissions to the Royal Adelaide Hospital for carbon monoxide poisoning was conducted from 1986 to 1989. Twenty-five patients left hospital with persistent symptoms and signs of this poisoning. Five subsequently recovered. Twenty-four other patients, who were well when they left hospital, did not attend for a review one month after discharge. Extensive neuropsychiatric testing at this time showed 32% (24 of 76) had obvious sequelae of their exposure. Overall, the frequency of neuropsychiatric sequelae in the patients who only received oxygen at atmospheric pressure was 63% (N = 8) on discharge and 67% (N = 6) on one month follow-up. The frequency of sequelae among those who were given one hyperbaric oxygen treatment only was 46% (N = 24) on discharge and 50% (N = 20) on one month follow-up. In contrast, the frequency of sequelae in patients who had two or more hyperbaric oxygen treatments was only 13% (N = 68) on discharge (P less than 0.005) and 18% (N = 50) on follow-up (P less than 0.005). the frequency of sequelae was also significantly greater if hyperbaric oxygen was delayed (P less than 0.05). No markers of severe poisoning could be identified.

Adolescent↗
PubMed1991

The P50 is reduced in critically ill patients.

A prospective study was designed to measure the P50 in 20 critically ill patients, and compare it with the P50 measured in 20 normal individuals. Arterial blood gases, lactate, haemoglobin (Hb) and phosphate (PO4) levels were also measured and compared with the P50 in the critically ill patients. The mean P50 of the critically ill patients was 24.5 mmHg (SD +/- 2.9) and was significantly lower than the mean P50 of 26.2 (SD +/- 2.2) in the normal individuals (p less than 0.05). In the critically ill patients, strong correlations were observed between the P50 and the arterial pH and base excess (BE) levels, with coefficients of 0.79 and 0.69 respectively whereas correlations between the P50 and arterial oxygen tension (PO2), carbon dioxide tension (PCO2), lactate, Hb and PO4 levels were poor, with correlations of 0.001, 0.008, 0.07, 0.13 respectively. It is concluded that the P50 is commonly reduced in critically ill patients, and has a strong correlation with arterial pH and BE.

Adult↗
PubMed1991

A comparison of the performance of 20 pulse oximeters under conditions of poor perfusion.

The performance of 20 pulse oximeters with finger probes was evaluated by comparison of their readings with directly measured arterial blood oxygen saturations. The samples were taken from patients who had undergone cardiac surgery under hypothermic cardiopulmonary bypass and had poor peripheral perfusion. The mean difference (bias, accuracy), standard deviation (precision) and drop-out rate for each pulse oximeter was determined. An overall ranking of performance of each pulse oximeter was calculated using five criteria (accuracy, precision, number of readings within 3% of standard, percentage of readings given within 3% of standard, expected overread limit in 95% of cases). Two pulse oximeters achieved a combination of accuracy and precision such that 95% of measurements would be expected to be within 4% of the co-oximeter value; these two also had the lowest drop-out rate.

Carboxyhemoglobin↗
PubMed1991

Potential errors in pulse oximetry. I. Pulse oximeter evaluation.

There is no absolute reference for oxygen saturation, although multiwavelength in vitro oximeters are accepted as the 'gold standard'. Regardless of whether fractional or functional saturation is used by manufacturers to calibrate their oximeters, evaluation against fractional saturation is recommended since this is the clinically relevant variable. The use of standard notation and comparisons based on bias and precision is recommended. The accuracy of pulse oximetry is intrinsically limited by the use of only two wavelengths, and is dependent on the initial calibration population. The empirical algorithms used to convert the signal to its 'readout value' and the quality control of hardware may both be important sources of variability between oximeters. Change in blood temperature may introduce errors in pulse oximeter and in vitro oximeter saturation readings, but these will be clinically insignificant. Changes in blood pH should not decrease pulse oximetry accuracy.

Humans↗
PubMed1991

Potential errors in pulse oximetry. II. Effects of changes in saturation and signal quality.

The published studies of pulse oximeter performance under conditions of normal, high and low saturation, exercise, poor signal quality and cardiac arrhythmia are reviewed. Most pulse oximeters have an absolute mean error of less than 2% at normal saturation and perfusion; two-thirds have a standard deviation (SD) of less than 2%, and the remainder an SD of less than 3%. Some pulse oximeters tend to read 100% with fractional saturations of 97-98%. Pulse oximeters may be suitable hyperoxic alarms for neonates if the alarm limit chosen is directly validated for each device. Pulse oximeters are poorly calibrated at low saturations and are generally less accurate and less precise than at normal saturations; nearly 30% of 244 values reviewed were in error by more than 5% at saturations of less than 80%. Ear, nose and forehead probes respond more rapidly to rapid desaturation than finger probes, but are generally less accurate and less precise. Ear oximetry may be inaccurate during exercise. Low signal quality can result in failure to present a saturation reading, but data given with low signal quality warning messages are generally no less accurate than those without. Cardiac arrhythmias do not decrease accuracy of pulse oximeters so long as saturation readings are steady.

Animals↗
PubMed1991

Pulse oximeter probes. A comparison between finger, nose, ear and forehead probes under conditions of poor perfusion.

The performances of 10 pulse oximeters using finger probes were compared with the same pulse oximeters using alternative probes (eight finger probes, two nose probes and a forehead probe) in poorly perfused patients. All readings were then compared with directly measured arterial blood oxygen saturations. The mean difference (bias, 'accuracy'), standard deviation (precision) and 'drop out' rate for each pulse oximeter combination was determined. An overall ranking of performance of each pulse oximeter was calculated using five criteria (accuracy, precision, number of readings within 3% of standard, percentage of readings given within 3% of standard, expected overread limit in 95% of cases). Nose and forehead probes performed poorly. Some ear probes performed well compared to some finger probes, but the overall performance of probes in other sites compared to finger probes was worse, (p = 0.05). Two of eight ear probes and no nose or forehead probes would be expected to be within 4% of the reference value in 95% of readings. The use of finger probes rather than probes in other sites is recommended in the patient with poor peripheral perfusion.

Adult↗
PubMed1991

Potential errors in pulse oximetry. III: Effects of interferences, dyes, dyshaemoglobins and other pigments.

Electrosurgery, patient motion and some types of lighting can cause errors in saturation readout; it is recommended that probes should be shielded from ambient lighting. Intravenous dyes can introduce gross but transient errors, which may also be present in in vitro measurements. Carboxyhaemoglobin causes overestimation of fractional saturation by an amount less than, but possibly close to, the percent of carboxyhaemoglobin present. Methaemoglobin causes the pulse oximeter readout to tend towards 85%. Fetal haemoglobin and bilirubin introduce no significant error, although they may interfere with in vitro measurements. Skin pigmentation can result in a slight decrease in accuracy. Nail polish may cause up to 6% underestimation of saturation; it is recommended that probes should be mounted sideways on fingers with nail polish or long nails. Adhesive tape or a vinyl glove across the probe has no demonstrable effect on accuracy. A blood sample should be analysed by a multiwavelength in vitro oximeter when an erroneous pulse oximeter reading is suspected, although errors may be introduced in the in vitro reading by fetal haemoglobin, bilirubin and intravenous dyes.

Coloring Agents↗
PubMed1990

An acute pain service in an Australian teaching hospital: the first year.

The Acute Pain Service began at the Royal Adelaide Hospital in April 1989. Funding, education programmes, policies, procedures, protocols, techniques (particularly patient-controlled analgesia, epidural opioid analgesia and subcutaneous morphine therapy) and daily organisation of the service are described in this article, and the experience with the 1053 patients referred to the Service during the first year of operation is reported. The occurrence of major complications was small. Mild-to-moderate respiratory depression occurred in four (0.5%) of the 747 patients who received patient-controlled analgesia and in none of the 177 who received epidural opioids. Five patients receiving patient-controlled analgesia had persistent nausea/vomiting; 320 (35%) of all patients receiving patient-controlled analgesia or epidural opioids suffered nausea/vomiting that required no treatment or was alleviated by treatment with an antiemetic. Around 13% of patients reported mild-to-moderate itching. In our experience, the combination of appropriately trained nursing and medical staff, standardised orders and procedures, and proper supervision can lead to safe, more effective management of acute pain.

Acute Disease↗